1. Field of the Invention
The present invention relates to a fluid injection valve, for example, it is applicable to fuel injection valve for injecting fuel into internal combustion engines for automobiles.
2. Description of the Related Art
As a conventional type of the fuel injection valve used in internal combustion engines, the electromagnetic fuel injection valve is known as disclosed in the unexamined Japanese Patent Publication No. 3-31570.
This fuel injection valve, as shown in FIG. 8, the needle 1 is movably contained within the body 4. When the electromagnetic coil 33 is electrified, the needle 1 seated on the valve seat at the bottom of the body 4 is attracted upwardly. At this time, a gap is formed between the needle 1 and the valve seat, through which fuel passes, and fuel is injected from the fuel injection port 36 formed at the bottom of the body 4. Fuel injection continues while the electromagnetic coil 33 is electrified, and after the termination of electricity supply, the needle 1 is seated again on the valve seat and the fuel injection stops. The above needle 1 is slidably disposed in the inner surface of the body 4 and axially guided in two guide portions 2, 3. The needle 1 also has a flange 5 in an upward position of the guide portion 2. The flange 5 is formed in a hollow disk shape so as to face a spacer 6 to form a gap therebetween. This flange 5 collides with the spacer 6 when the needle 1 is attracted by electromagnetic force, thereby the upward movement of the needle 1 being limited. The flange 5 and spacer 6 comprise a stopper of the needle 1. The amount of the movement of the needle 1 by electromagnetic force (the amount of full lift) is determined by the distance of the predetermined gap between the flange 5 and the spacer 6.
During this operation, the needle 1 is tilted relative to its axis by the influence of an outer force such as the spring which applies pressure toward the valve seat, and is maintained in contact with the guide portions and the inner surface of the body. When the needle 1 is attracted upwardly while remaining in such tilted condition, the flange 5 collides with the spacer 6 on one side at first, as shown in FIG. 9A. The triangles shown in FIGS. 9A and 9B indicate the contact points between the guide portions and the inner surface of the valve body. After some interval, the top surface of the flange 5 comes entirely in contact with the bottom surface of the spacer 6, as the needle 1 is further attracted by electromagnetic force. At this time, the needle 1 attempts to rotate counterclockwise with the one-sided contact point as the fulcrum. However, as the guide 2 is in contact with the inner surface of the body 4, the needle 1 is not able to rotate, and the flange 5 is finally shifted to the right as shown in FIG. 9 in the position of one-sided contact, the surface of the flange 5 entirely comes in contact with the spacer 6.
Thus, as the flange 5 gouges the bottom surface of the spacer 6 in such a manner, the stopper suffers wear. This stopper wear may cause the instability in the injection quantity or a degradation in durability.
For solving such problems, it should be necessary to maintain the gap between the guides 2, 3 and the inner surface of the body 4 at an extremely accurate clearance. As a result, a high-precision machining becomes necessary, which causes another problem.